The present invention relates to a method of preparing semiconductor structures and devices which utilize polymeric dielectric materials. In particular, the method permits fabrication of semiconductor structures bearing conductive patterns or connections and utilizing polymeric dielectrics such as polyimides.
Methods of manufacture of semiconductor devices are frequently comprised of a series of steps during which layers of various materials are applied to the semiconductor structure. Some of the layers remain as part of the device at the end of manufacture, while others are utilized as masking for subsequently applied layers and are removed prior to completion of manufacture. Frequently removal of a masking material is achieved by use of a solvent which dissolves the masking material while leaving surrounding materials, which are intended to be a permanent part of the semiconductor device, intact.
In some cases the materials which are intended to become a permanent part of the semiconductor device are sufficiently similar in nature to the masking materials that they are affected by the solvent used to remove the masking material. This is particularly true when polymeric materials are utilized both as permanent functional components and as masking materials. As a result, the polymeric materials intended to be a permanent functional part of the semiconductor device become contaminated with solvent used to remove the polymeric masking materials and do not function as intended. In addition, because the solvents used to remove the masking are frequently volatile, they tend to evaporate and migrate over time, so that the functioning of the polymeric materials within the device and thus the functioning of the device itself changes over time.
Examples of processes utilizing multi-layer material depositions and masking layers which are subsequently removed include U.S. Pat. No. 4,256,816 Dunkleberger, and U.S. Pat. No. 4,224,361 Romankiw (assigned to the assignee of the present invention). Interest in replacing traditional inorganic dielectric materials in semiconductor devices with polymeric materials, e.g. as device dielectric isolation layers, trench dielectric, and interlevel passivation layers, has been significant due to improved ease of fabrication and potentially better thermal and electrical properties obtainable when the polymeric materials are used. This interest is manifested in the form of U.S. patents which disclose the use of polyimides, polyimide-polyamide or like materials as insulating or passivating materials in electronic components. Among such patents are: U.S. Pat. No. 3,700,497 Epifano et al; U.S. Pat. No. 3,846,166 Saiki et al; U.S. Pat. No. 3,486,934 Bond; U.S. Pat. No. 3,515,585 Chamberlin et al; U.S. Pat. No. 3,985,597 Zielinski; and U.S. Pat. No. 4,367,119 Logan et al.
Due to the interest in using polymeric materials such as polyimides as dielectric materials in semiconductor devices, it is necessary to provide a method of preventing contamination of such polymeric materials by the solvents used in the fabrication process. The present invention solves this problem by providing for use of a substitute polymeric material as a space holder and surface protective entity during certain processing steps, with subsequent replacement of this substitute material using the desired polymeric dielectric.